Treatment of phosphates



E. C. SOPER.

TREATMENT OF PHOSPHATES.

APPLICATION FILED NOV. 11. 1918.

1,431,456 Patented Dec. 5, 1922.

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lgldhtdt @ATENT KDFFHCE ELLIS C. SOPER, 03F CEATTANOOGA, TENNESSEE.

TREATMENT OF PHOSPHATES.

Application filed November 11, 1918. Serial No. 261,960.

To all euhom it may concern Be 1t known that l, ELLIS C. Sornn, a citizen of the United States, residing at Chattanooga, in the county of Hamilton and State of Tennessee, have invented certain new and useful Improvements in the Treatment of Phosphates, of which the following is a specificatlon.

My invention relates to new and useful improvements in the treatment of phosphates, and particularly relates to the conversion of insoluble phosphates, for example, calcium phos hate, phosphateof iron, and phosphate 0 aluminum, or combinations thereof, into citrate soluble form, rendering them suitable for use as fertilizers.

The invention is equally a plicable to the treatment of phosphates 0i calcium, such as are known as 'll ennessee phosphates and Florida phosphates; phosphates of iron and aluminum which occur principally in the JV est Indies, and phosphates of aluminum known asapatite. The invention is also applicable to the treatment of so'called soft phosphates which are found in large quantities in Florida, and low rade phosphates,

4 which do not contain 'su cient phosphoric acid for commercial threatment by processes hitherto known. I The invention consists in the improvements to be more fully described hereinafter, and the novelty of which will be particularly pointed out and distinctly claimed.

in my prior application, Serial No. 243,- 678, which was filed in the Patent @fiice July 6, 1918, l have describeda process of rendering insoluble phosphatic material citrate soluble, which consists, briefly, in forming an intimate mixture of the material containing the insoluble phosphoric acid with a reagent, such 'as an alkali metal salt, such intimate mixture being made by finely rindin the mixture of materials with t e addition of water to such an amount that the mixture is fluid. The reagent is then thoroughly disseminated throughout the mass of phosphatic material and is brought 'into intimate contact therewith. This mixture is then treated at the proper temperature, preferably in a rotary kiln. Treatment of the fluid material in a rotary kiln, however, is dificult, because the wet or fluid mixture adheres to the inner lining of the kiln at the inlet portion thereof, resulting in building up, brown as ringing in rotary kiln practice, of the mixture on the inner surface of the kiln to such an extent that said material will not pass rapidly through the kiln and be properly subjected to the heat thereof. In accordance with my prior invention, in order to overcome this difficulty, a stiffener or drier was added to the mixture, whichreduced the initial fluid condition to a substantially plastic state, and briquettes were formed from this material which could be treated in the kiln.

lln accordance with my present invention the entire process is carried out with the materials in a dry condition. I have found that the insoluble phosphoric acid of a phosphatic material may be rendered citrate soluble by grindin together the phosphatic material with an a kali reagent such as sodium bi-sulphate, known as nitre-cake, or sodium sulphate, and a carbonaceous material, such as saw-dust or corn-cobs ground into a fine condition, thoroughly mixing the material's, preferably by grinding, after which a limited amount of water which is insuliicient in amount to destroy the dry condition of the material may be added, and finally calcining the mixture at a high temperature, preferably at a temperature rangin from 2400 to 2600 F.

l hile l have found, in practice, that this method, as at present practiced, will not give so high a percentage of citrate soluble phosphoric acid as the method described in my prior application, in which the ingredients are mixed with water, I have found it desirable, under some conditions, to use the present process, because of the saving edected in the cost of fuel. For example, in accordance with the process disclosed in my prior application, as at present practiced, there remains about 1% insoluble phosphoric acid and if a phosphate contains, say, 30% phosphoric acid, the available citrate soluble phosphoric acid will be 29%.

the materials in a dry condition -that is, when no appreciable amount of water is added-then the insoluble averages about 3% to 4c%, maki ng the percentage of available citrate soluble phosphoric acid 26% or 27%, and this percentage is sufiiciently high to make the process entirely commercial under certain conditiom."

The phosphatic material may be, for example, phosphate of calcium, such as Florida pebble phosphates, ground either together or separately with a proper reagent; for example, sodium sulphate, sodium bi-sulphate, or sodium carbonate, in varying pro-. portions, depending upon the quality of the phosphate material used as regards its phosphoric acid content. For example, where the phosphatic material is a phosphate of calcium, such as is known as Florida pebble phosphate, which may contain approximately 31% phosphoric acid in an insoluble form, the rock is pulverized with 20% to 40% of sodium bi-sulphate, or nitre-cake, to a fineness of about 98% or more through a sieve of 100 meshes to the inch. If saltcake (sodium sulphate) is used, a relatively smaller percentage is required-for example, about 15 to 30%. The best results are s'ecured when the silica in the phosphate is less than 8%. If it exceeds this amount, then it is desirable to add calcium carbonate in liberal amount to combine with the silica, as otherwise a tendency to fuse is present. Also, the clinker is much softer and easier to grind when calcium carbonate is added. Good results can be'obtained with the addition of this material alone, without the addition of alkali material or carbonaceous material.

In carryingoutmy process I may proceed as follows:

Any suitable phosphate rock, say, a Ten- 3 nessee rock, of the following analysis may be used: Phosphoric acid, total 32%; silica 10%; iron and aluminum, 7%. Any appropriate amountof this rock is taken and to the same the following materials may be added: Sodium bi-sulphate (nitre-cake),

22%% by weight of the phosphatepcalcium carbonate (95% purity or better), 7-%% by weight of the phosphate; saw-dust or ground cobs, 7%% by weight of the phosphate. Roughly, the saw-dust or corn-cobs may be added to the extent of one=third of the-total the, tube-mill.

volume of the mix and ground together in The cobs take up a certain amount of moisture from the mixture in the tube-mill; about one-half their weight.

I Then more saw-dust or corn-cobs are added until they constitute about one-half of the mixby volume. The materials must be dry and may be finel ground separately a'nd then mixed; but t. ezbest results can be ob-' tained 'onl when the grinding is done in a tube-mill m which all of the materials are fed and ground together. The fineness must be such that 96% to 98% or more of the material would pass a 100-mesh sieve, though 'falr results maybe had when the fineness is lower than this.

After the raw material has left the tubes mill, and after it has been mixed with the corn-cobs, the addition of approximately 10% of firing rotar as'mao to 20% of water ma be made. This addition appreciably re uces the loss indust, and also assists in eflecting the porous condition which is desired for complete action in the kiln. At the same time, the amount of water added is insufficient in amount to destroy what I have described as the dry condition of the material,as the amount of Water is insuflicient to bring about a plastic condition of the material, which retains its powdered condition. a

The ground material is now fed by a mechanical feeder'into the upper or feed end of a rotary kiln containing a basic or neutral lining and in the lower end of which is a flame produced-as in the ordinary method kilns. The combus ible material inthe mixture first burns out quite rapidly at the same time the sulphur gas is driven off from the bisulphate, leavmg the sodium free to act upon the phosphate. The temperature at which the final conversion of the phosphate to citrate soluble takes place is from 2400 to 2600 F. The resulting sintered material is now ground to afiness of at least through a 100-mesh sieve. The contained phosphoric acid'may nowbe about the following-analysis: Total phosphoric acid, 32%; insoluble phosphoric acid, 4%; available phosphoric acid, 28%.

The bi-sulphate hassubstantially all been decomposed and, of course, the combustible matter has completely burned out. There has been practically no dilution. If one ton. of phosphate is treated, then there is pro duced one ton of product containing the original 32% or 32 units of phosphoric acid.

In the present method of manufacturing,

acid phosphates containing more than 5% iron and alumina cannot be used. In this processthere is no efl'ect whatever on the product with greater and varying percentages ofironand alumina. The calcium carbonate is added when the silica in the phosphate exceeds 8% and it also assists in producin a softer product; i. e., reduces the cost 0 final grindin The combustible added may be in the form of sawdust, coal with a low ash content, or coke with a low ash, or any other carbonaceous or combustible material. The addition of this material is not absolutely necessary, but it increases the fuel efiiciency of the process, and also assists in effecting a bettermechanical condition of the material in the feed end of the kilnor furnace by creating a certain porous condition. i i

The use of corn-cobs as the combustible is advantageous, since they contain a certain, amount of .potash, which remains'asash the water soluble form in the finished product and improves the quality of the material as a fertilizer. r

In the accompanying drawings 1 have Monroe shown a rotary kiln which is suitable for carrying out the calcining part of the proctaken through the box at the front end of the kiln, and Fig.3 is a view similar to Fig. 1 but showing only a part of the kiln and showing a modified chute for feeding the material to the kiln.

Referringnow, to the drawings, and first to Figs. 1 and 2, 10 is a hopper into which the materials which have been thoroughly mixed in accordance with the process described above, are introduced. The hopper communicates, by means of a tube 11, with the front end of the rotary kiln 12, the tube passing through a central opening 13 at the front end of thekiln. In the form shown in Fig. 1, in which the tube 11 is substantially horizontal, a screw feed 14, or its equivalent, is used for feeding the material from the hopper 10 to the front end of the kiln. The kiln may be mounted on roller bearings 15, which are supported in pedestals 16, carried on supporting blocks 17. Metallic rings 18 are preferably secured peripherally on the outer face of the kiln 12 and engage the rollers 15. The kiln may be rotated by means of a gear-wheel 19, also'secured on the outside of the kiln, which is driven by any suitable mechanism (not shown in the drawings). The front end of the kiln l2 communicates through the opening 13 with a smoke or dust-box 20, to which a stack 21 may be secured and which is here shown as integral therewith. A baille 22, which is here shown generally semi-circular in form, isdisposed in front of the upper portion of the opening 13 and immediately above the tube 1%. This baflle is connected through a cord or cable 23 passing over pulleys 24 to acounter-weight 25. It will be understood that by adjusting the kiln 12 may be regulated. It will he noted that the comparatively small opening which is provided at the front end of the kiln leaves a fairly high retaining ring 26, which prevents an excessive amount of dust from the charge of material being treated inthe kiln from passing to the stack and thus being lost,

Tn Fig. 3 is shown a slight modification of the arrangement for feeding material to the kiln. The tube 11 is there arranged in an inclined position, so that the material is fed from the hopper 10 to the kiln by gravity, and without any positive feeding device.

It will, of course, be understood that a suitable burner will be disposed at the mouth of the kiln for introducing a flame into the kiln and heating the charge therein.

What I claim and desire to secure by Letters Patent of the United States is 1. The process of treating phosphatie material to render the contained phosphoric acid citrate soluble, which consists in separately grinding carbonaceous material and a mixture of phosphatic material and an alkali-metal reagent, intimately mixing said materials in a dry condition, adding water to the mixture in an amount which leaves the mixture in a powdered condition and calcining the mixture at a temperature of 24:00 to2600 F. i

2. The process of treating phosphatic material' to render the contained phosphoric acid citrate soluble, which consists in intimately mixing with the material an alkalimetal reagent and carbonaceous material, adding water to the mixture in an amount which leaves the mixture in a powdered condition and calcining in a dry condition and at a temperature suficient to convert the phosphatic material to citrate soluble material. I i v 3. The process of treating phosphatic material to render the. contained phosphoric acid citrate soluble, which consists in intimately mixing with the material an alkalirnetal reagent and ground corn-colos, adding water to the mixture in an amount which leaves the mixture in a powdered condition and calcining the mixture in a dry condition at a temperature suflicient to convert the phosphoric material to citrate soluble material.

4:. The process of treating phosphatic ma terial to render the contained phosphoric acid citrate soluble, which consists in inticonvert the phosphatic material to citrate soluble material. C I

5. The process of making a fertilizer which consists in intimately mixing a phosthe position of the bathe 22 the draft through phate rock, an alkali-metal salt and a carbonaceous material containin otash add- 'ing water to the mixture in an amount calcining the same at a high temperature.

7 The process of treating phosphatic material to render the contained phosphoric acid citrate soluble, which consists in intimately mixing phosphate rock, sodium bisulphate to the extent of substantially 22%% by weight of the phosphate, and fine carbonaceous material, all in a dry condi lltl tion, adding water to the mixture in an amount which leaves the mixture in a powdered condition and calcining the mixture at a high temperature.

8. The process of treating phosphatic material to render the contained phosphoric acid citrate soluble, which consists in intimately mixing phosphate rock, sodium bisulpha'te to the extent of substantially 22%% by weight of the phosphate, and fine carbonaceous material to the extent of sub stantially 75% by weight ofl the phosphate,

adding water to the mixture in an amount which leaves the mixture in a powdered con-v dition-and calcining the mixture at a high temperature. 7

9. The process of treating phospliatic material to render the contained phosphoric acid citrate soluble, which consists in intimately mixing with the material a' reagent and carbonaceous, material in a dryflcondition, adding water to the mixture in an amount which leaves the mixture in a memes carbonaceous material containing potash adding Water to the mixture in an amount which leaves the mixture in a powdered condition, and then calciningthe mixture at a high temperature.

11. The process of making a fertilizer which consists in intimately mixing a phosphatic material, an alkali-metal salt and ground corn-cobs', and then calcining'the mixture at a high temperature. I

In testimony whereof I have hereunto signed my name in the presence of two subscribing witnesses.

Witnesses v ERNEST ArrLEBY,

Donems l Em 0. some; 

